Changes in ecosystems after the removal of stress provide a rich source of information for conservation science. We used a long‐term regional data set on the performance of white sucker (Catostomus commersonii) collected before and after the closure of a pulp mill to explore recovery in fish. Physiological indicators, including liver enzymes and plasma steroids, showed some compelling changes after the closure of the mill consistent with reduced exposure to pulp mill effluent but did not unequivocally demonstrate recovery. However, persistent signals in these fish may indicate effects of impoundment or discharge of sewage. We also used quantile regression with environmental covariates and bootstrap iteration to determine if systematic variation remained in relative body weight, liver weight, and gonad weight. In fish formerly exposed to pulp mill effluent, we found evidence of improvements (male gonad weight and liver weight of males and females), degradation (gonad weight of females), and no change (body weight). Although the observed patterns may be associated with closure of the mill, some differences were also found at regional locations, suggesting roles of additional stressors and challenging the clear association of change at the Mattagami River exposure site with the closure of the mill. However, fish captured at this location show responses consistent with regional locations, suggesting no residual impacts and highlights the challenges of identifying changes in fish even after large and known interventions. Environ Toxicol Chem 2021;40:162–176. © 2020 SETAC

中文翻译：

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加拿大安大略省北部一家漂白硫酸盐纸浆厂关闭前后鱼类健康的长期研究

消除压力后生态系统的变化为保护科学提供了丰富的信息来源。我们使用了关于白色吸盘（Catostomus commersonii ）性能的长期区域数据集) 在纸浆厂关闭之前和之后收集，以探索鱼的恢复情况。生理指标，包括肝酶和血浆类固醇，在工厂关闭后显示出一些引人注目的变化，与纸浆厂废水的暴露减少一致，但没有明确表明恢复。然而，这些鱼的持久信号可能表明蓄水或排放污水的影响。我们还使用带有环境协变量和自举迭代的分位数回归来确定系统变异是否仍然存在于相对体重、肝脏重量和性腺重量中。在以前接触纸浆厂废水的鱼中，我们发现了改善（雄性和雌性的雄性性腺重量和肝脏重量）、退化（雌性的性腺重量）和没有变化（体重）的证据。尽管观察到的模式可能与工厂关闭有关，但在区域位置也发现了一些差异，这表明额外压力因素的作用并挑战了 Mattagami 河暴露地点的变化与工厂关闭之间的明确关联。然而，在该地点捕获的鱼类显示出与区域地点一致的反应，表明没有残留影响，并突出了即使在大规模已知干预之后识别鱼类变化的挑战。环境毒理学化学2021；40：162-176。© 2020 SETAC